The invention relates to the fields of simulation and system optics and is particularly useful in training personnel for vehicular control reaction to a series of image displays depicting problem conditions.
In the prior art, devices incorporating a heads up display system have utilized either screen projection means or a beam splitter to bring the image to the heads up viewing position of the observer or trainee. Problems related to the prior art devices include the element of time in switching from one image to another, the elements of background interference, low contrast, variations in light intensity levels and the effect on eye muscles of having to react to apparent variation in image distance.
In the present invention the provision of adjustable polarized light valves for controlling light rays projected through a holographic lens as a window to the eye of an observer eliminates the disadvantages mentioned above. Thus, in the polarized light valve concept since the image light source is on all the time, the light valve provides an instant-on feature. There is no delay time required for bulb warm up. The light valve concept provides a perfectly black background from any and all channels where the valve is in closed position. This feature is critical since any stray light impinging on a holograhic lens will be directed into the trainee's eyes as a background flare, thereby reducing image contrast and decreasing trainee's eye pupil size. This decreases his ability to recognize targets. Image enhancement is thus obtained. The invention further provides via the adjustable polarized light valves and a light level metering means the ability to control light level during image change on any one or more channels and thus avoid muscle strain and time lag to accommodate the eye to a different light level. The polarized light valves also enable a selected variation of light level to depict conditions of day, night, fog, shade, etc. A further and important feature of the invention is the ability to introduce a plurality of more than two input channels from image sources and to maintain all images at infinity such that again the eye muscles need not be employed to accommodate to close and distant objects. The eye muscles thus remain relaxed. In a further aspect the invention provides trace recording means coordinated with the programmed light channel means to provide a record of trainee performance trace in relation to optimum performance trace on the same record.